Vacuum tube oscillator



July 15, 1952 H. v. NEHER VACUUM TUBE OSCILLATOR 2 Sl-IEETS--Sl-IEET 2 Filed Jan. 13, 1944 INVENTQR.

HENRY V NE H E R B 4 @4de nvr/ve) Patented July 15, 1952 y UNITED STATES VACUUM TUBE OSCILLATOR v Henry VV. -Neher, Arlington, 'lVIass.,`assirgll-iox',` byE mesne assignments, to the l United States. of America as represented' by :the Secretary of Warr Application January 13, 1944, Serial No.y 518,135 Y 5 claims. (o1..s15--5 TheA invention described herein may be manufactured and .used by or for the Government for governmental purposes', without the payment to me or" any royalty thereon.

This invention relates to vacuum tube oscilr latorsuseful at frequencies of the order of 30,000

' megacycles.

As is well known, conventional vacuumV tube structures with electrostaticv grid control become inoperativeat ultra high frequencies due principally to` the transit time of electrons. In order to make such tubes operate, the electron path between cathode and anode may. be' designed in part orv in whole .as Va resonant chamber orl cavity for the frequencyde- .quite easylfor one tube VAto. be misalined in 'the frequencyspectrum. It becomes `of-great'mportance therefore to provide a tube structure which is susceptible to frequency tuningzovera definite range.

This invention provides a tube structure having tuning means built in` so that the resonant characteristics of the cavity resonator may be Yariedfrom outside the tube. The structure provided issimple. may be usedin quantity production and' results in a tube having highly desirable advantages. l In general, the inventionnpr'ovides a gcavity resonator at 4least one wall of :which is deformable. The deformation may be adjustedfjrom punie@ iheiubeby 'Suitable pressured; .an elas- :i llb ism/.G1026 0151er; heating: current-1 passed throughsuitable leads into the tube interiorpand @erige/Qn thermally ,resppnsive materiel cooperating ,with Athe l deformable. wall.; 'lliusaule4 .fixed tuning ofthe cavity resonatorv may; be :adjusted within :limits orthe; cavity:l may/.be continuously timed .over inalienable-range to nd afdesired o perating'f-requency, 1:' Another determinant for vproper"tubepperation lis-;the,fpotential gradient.: existnswithn various such atubeA must' provide space current at a high voltage. Itis quite important that generation of. space current be efficient .toeliminate waste of power. The invention hereinafter described provides an electron gun delivering practically all electrons emitted lfromthe cathode surface as a .fine beam travelling` at a high velocity.

Referring now to a sectional, elevation.. along line I'-`I lof Figure. 3. Figure 2.shows a.; sectionalongm2-'2` of Figure l. Figure 3 showsa sectionalong 3-53 of Figure l.. Figure 4 showsa section along 4-..4 vof. Fig ure 1;:1` Figure 5 is. an enlarged section ofthe-high frequency output electrode and cable, and Figure 6 is anl enlarged sectional perspective showing the resonant `cavityand. various control electrodes.

The vacuum y generally cylindricaly metalevacuated .container I0 of the type on the market at present. Inas.- much as base connections are well known, no attempt is .made tdshow. them.. Containern made. of any suitable'metal usually-.iron `and hasldisposedwithin. it an Fannular' fr'amev II, v

preferably ofzmetal. FrameII may have any desired :shape vand as shown'v here consists of a bottom annular ring I2, a central section I3 cut away to save metal, and a top annular section I4. terminating in an annular flange I5. 'The entire tube structure may be supported by .framework II.; 11. Y

' Snugly mounted within annular ring' I2 is a heavy metal base plate 20.. Base plate 20 may be locked to irame'II prior to insertion within envelope' I0 by means of vone or more bolts. 2| extending 'through annular ring I2 and into base plate 20. Base-plate 20- may be made ofany sutablef'metal preferably av relatively soft metal which'may be fabricated easily.-V 'Thus base plate 20 may? adv'antag'e'o'uslyv be fabricated :from copper.. ,"AsfshowninFigure 1,1ba'se plate/'20 has a;v relatively massive thickness and may have a pluralityof apertures`22 and 23 vthroughwhich leads may pass. In 'addition' tov these f clearance apertures,"base plate v20 may have a series-.here shown as six-ofapertures 24 to 29. inclusive.

As is clearly evident from'Figure.3,`base plate 20 is circular and the various apertures are symmetrically disposed. Base plate 20 is provided with twoannular grooves orv channels`30 and -3I on opposite faces thereof, groove 30 being on the...bot t0m face vvhilefgroovel' iszon the :top face. .-''lheqbottom` face of base.l plate 20 has. .a

vcenter thereof cut .awaygto form aigenerallycup the drawings, Figure 1 shows tube. is 1 preferably Yformed of a shaped recess 32, the vcenter of(` which is cutout to form a generally conical chamber 33 passing through the entire base plate. Base plate 20 has the top face thereof cut away `at the center to form aY deep generally doughnut shaped chamber .34.v As is clearly evident in Figure l, conical" chamber 33extending up into doughnut shaped chamber 34 results in a generally hollowfaper.-v

^ 8! is welded to conductor 30 and the ends of wire are spot welded to ilangei. Lead 82 may be used for supplying heating current to lament 8| vwhen such current is desired. As wire 8| expands,

Y bowl-spring 85'i`orces diaphragm down.

tured cone 35` whose apex 36 is disposed'av short y f distance below the plane ofv the ltop face of base plate 20.

Disposed against the bottom face of `base plate 20 is an annular insulator 38 followed by an an-v VTV*spot welded to diametrically'opposite'points on `flange l5. Disposed aroundthe outside `of envelope shell Hl is a rigid Aclamping ring 90 having la pair of clamping screws 9| and 92 disposed along nular conductor 39 followed again by van annular^--f insulator 40 thence by an annular conductor 4|, thence again. by an annular insulator "42 and iinally by a relatively heavy fend .clamping plate' 43.A Similarly the top face of base plate has alternate annular insulatorsr45, 41, and 49 interf spersed with conductors 4S, 48,V and clamping plate f50. rigidly together by a seriesof'bolts here shown as `three Vin'number and disposed Vin apertures l25,

' 2'|,and.29. vInasmuch as these clamping bolts are metal andbecause of the high. potentials Vimpressed upon .the various metallic members, itis preferredto .cut away the: clamp rings 43 and 50 and all the intervening metal members, the eutti'ngawaygbeingaround thebolts. These cut- 1 ,.aways, indicated bynumerals .52 toit, inclusive,

provide a substantial surface path'falongrthe insulators 'and prevent breakdown. To `promote the ready assemblyof athe various y .partslalternate aperturesf24, 26, and' 28. are pro'- ivided, these .apertures being adapted to fit ac- Vou'ra'tely spacedrods in a jig'over which the vari-'- ous rmembers are threaded. Thus when the'as'- sembly is bolted, the jig may be removed without disturbing the alinement. In addition, these apertures providegas dispersal paths during evacuationf IA-nnularl metal membersaearriesia'metal focus-v tending-downwardly from annular metallic mem .ber 4|; iWithin" cathode 6| Athere maybe disposed -a heating filament 66.

Referring to the top face of base--plate-20,`

doughnut shaped chamber 34 is covered by agenerally corrugated metallic diaphragm of-exible materialsuch as copper or steel.A The peripheral vportion'of diaphragm 68 maybe spot welded-to the vtop fajce of base plate 20. Diaphragm 68 has a central 'aperture 69 collinear with'conical aperture ,36 anduisadapted tolcooperate with-.doughnut shapedccavity A36 to provide an adiustable:

resonant cavity., Above diaphragm S8 and insu,-

lated .therefrom is metal member 4.6'. x metal` member isfrigid and is provided withanaperture lmcollinearwith apertures 36 and 69. Adjacent to aperture Y'Hl are; clearance apertures 'll and v'|2. .r Above metal member46 isrmetal member 68 also rigid 'and havingclearance apertures 13 and 14 in line with `clearance.apertures and '|2. g

.In order to control the position of rdiaphragm 88, apairlof posts -15 and "I6 may be; spot-wielded on Vopposite sides of. central aperture.v 69.12 Posts l5 and 15 extend through :clearance apertures to.|4, inclusive, as shown; and extendiupwardly where the .free Vends .are joined by acrossV .piece -Rigidlygjoined to cross `Dfe :'|T| is a; push rod 1B i The entire Structurej is maintained Alsolfastened 4to vrod '18 is a bowed spring 85 of the shape shown whose free endsS and4 8l are the lring at an angle of 970 from each other. As

' shown in rFigureY 2, clamping ring 90 is somewhat .larger in diameterthan shell l0 and is rigid. enough so that application oik eitherrscrew al ori SZArnay'distort the shell along the two diameters. It iselear that as shown in Figure 2 screw 92 tends to squeeze shell l0 so that the distance between ends *86 and VB'l of the spring-is increased. This tends to drop rod 18 and thus moveflexible partition 68 down to reduce the volume of the cavity. By virtue of expansion induced by heating offilament 8| downward-movement of rod '18 may be additionally provided.V 1 Y A. i

For picking up oscillatory'energy from cavity 34, a cable structure shown in Figures 3 and 5-is provided. As shown in Figura; base plateV f2.0 isA provided .with a generally radial channelv exe tending `from cavity 34 outwardly through the tube. structure.k Spot weldedto shell I0 isacable structure comprising an outer metal sleeve 95.*ofY

any suitable shape and here shown as having .a

Vthreaded end 90. Within sleeve 95 are two bores 91 and 9B separated by annular metal partition 99. lPartitionll has rigidly mounted thereina relai .tively fine metal tube |00 adapted to t snugly within the channel formed in base plate 20. This metal tube |00 is adapted to extend through baseY loopflies ina 'plane generally parallel to the lengthr of theV tube and functions as a pick-up `electrode lfor ultra-high frequency energy.. It. is under.- stoodof course' that the dimension.l of -loop |03 together with the constants of the coaxial line and the Vresonant frequency of .cavity34-'all 'cooperate tofpicl: up oscillatory energy." Wire |02 kis carried by a heavy metal rod ||l5rigidly supported within sleeve'f95 by suitable means su'chfas av glass seal |06. Rodllftogether with sleeve 95 forms/a co"- axial cable and may/be dimensioned tofitastandi ard coaxial coupling. It is understood of course thatr the entire coaxial assembly is sealedproperly soi-that'a vacuum within Shelli |0may -be main!- tanedan ..1 p In practice, base Y'plateMZllx'naybe grounded. At .a highnegative potential thereto-"is cathode 6| whilea still greater negative potential may be impressed upon cylinder fr'the purpose Yof fol cussing electrons emitted fromirc'athode 6'|.'- The electrons are'emittedinith'e form of apencir'concentric with the axisfof thei-'s'tructure Aand-'pass through aperture 36 as a nebeam.- .Due tothe steep potential gradient existing betwe'encathode El land .base plate .20., .the electrons yare impelled atayhighvelocity to aperture '36. Betweena'perl The end Tof, |02A is'loopedY tends-toislow down the electrons'. Electrons vreflec'tedby reflector may then be accurately. fo.- cussedv by back-focussing electrodei 46; "atcathode potentialsubstantially,` and thus pass back into cavity 34. Thus velocity modulation of the electron stream in such a manner as to bunch the electrons and cause oscillation at high `frequency is brought about. oscillations arepicl ed up by loop |03 and conducted out.

- The combination of' cathode BI and focussing cylinder 60 provides at conical aperture 36 a fine uniform streamV of electrons moving ata. substantially `uniform velocity. 4'I he distance a'from aperture -36 to aperture 69 i's preferably .small compared to the wave length of oscillations. In other wordsthe transit angle.for distance a'. is small. 'Distance'b from aperture`69 to reflector i4! vis substantial in terms of wave lengthand transitiangle.V -Roughly a proportion of-about four to one-for the ratio of 'bovera maybeu'sed. "It is essential that symmetry'a'nd rigidityabe inherent inthe structure. Byzvirtue oflthe.v symmetryf'fquantity production may be obtained without serious impairment offqu'ality.I [In particular the alinement and symmetry of the elecxed tuning over a substantial range. However some fine rapid tuning may be desirable and this may be obtained by applying a slowly varying current to heating wire 80. Thus an alternating current of about ycycles per second may be used to determine if the ring tuning is near the desired frequency. The filament tuning covers a small part of the tunable range and may be used not only for exploring but also for fixed accurate tuning. This may be accomplished by maintaining a direct heating current in filament 8|.

What is claimed is:

1. A vacuum tube. oscillator for use in ultrahigh frequency comprising an evacuated metal envelope, said envelope containing the following elements mounted therein: a relatively massive block having fiat faces on opposite sides thereof, and a generally doughnut shaped recess cut in one face thereof, said block having a channel therethrough along the axis of said recess, means on the other face of said block, for generating and focussing a beam of electrons on said axial channel and disposed along the axis, a flexible cover plate on said first face above said recess, saidr cover plate having the edge thereof rigidly secured to said block covering said recess and forming a cavity resonator, said cover plate being flexible along the axis of said cavity resonator to vary the volume thereof, a bowed spring disposed within said metal envelope, a mechanical connection from said spring to said flexible cover plate positioning said cover plate in accordance with the condition of said spring, means on the outside of said metal envelope and connected to said tensioning means for distorting the same to transmit force to said bowed spring for adjusting the resonant frequency of said cavity resonator, and a pick-up electrode passing through said envelope and block into said cavity.

2. A vacuum tube for use as an oscillator for ultra-high frequencies, said tube comprising a flexible metal envelope, said envelope being evacuated and supporting the following elements: a

massive. metal blockhaving flatfaces.: onxopposite sidesithereof, .one .of said faces. being. cutfaway forming a generally .doughnut sh'ape'drecess on one. side-,..the*other` .face being cut away :forming agen'erallyconical recess "on the'other'sde sym..- metrically `disposed with :respect tosaid first -recess,f a .channel along .the alined' axes of said tube recesses andapassing'through said':bl'ock, means on theotherf side of said block, foragenerating and .focussing a beam Aof electrons on said chan'- nel 1 for'` passage through .said .f block, :aeaflexible metalfcover 'plate :disposed on. saidzzone :facefzof said block coveringsaid doughnut shaped recess totransformjhe' samel intoifa cavity resonator. 'saidcover plate ,beingrigidly' andi conductively securedy to .saidr block along the'bounda'ry -o'f said recess. said cover plateghavingfan aperture therethrough alongthefaxis .of said chamber through which the' generatedf electron beam normally passes, a. reflecting plate insulatingly carried .by said blockl adjacent .tofand .spaced-j from; said cover plate, a push-'rod fastenedto said' coverplate and passing through said reflector plate, a bowed spring anchored within saidenvelope to :which said :push rod is vfastened, means encompassing said envelope for distorting. 'said envelopeto control said i's'pring whereby the lpositionxol .;said coveivplate isadjustedto control the volumeof Vsaid cavity resonator, a pick-up electrode passing through said block and into said cavity for conducting oscillatory energy from said vcavity resonator outside of said tube passing through said envelope for said' electrodes.

3. The structure of claim 2 wherein an additional spring is anchored within said envelope, said additional spring being connected to said push rod and acting in opposition to said bowed spring and means connected to said additional spring adapted to be energized from outside said envelope for heating said additional spring to vary the tension thereof for controlling the movement of said cover plate.

4. A vacuum tube comprising an envelope of flexible metal, said envelope being evacuated and containing within it the following elements supported therein :v a relatively massive block of metal having two flat faces on opposite sides, said block having a generally doughnut-shaped recess cut into one of said faces and a channel through -said block axially of said recess, means on the other face of said block for generating and focusing a beam of electrons to pass along said axial channel, a flexible metal cover plate upon said recess to change the same to a cavity resonator, said cover plate being rigidly fastened to said block at the periphery of said plate, spring means anchored to said envelope and connected to said cover plate for biasing said iiexible cover plate, said spring biasing means including a bowed spring disposed within said envelope and anchored thereto and connected to said cover plate, means connected to said spring biasing means adapted to be energized from outside said envelope for heating at least one part of said spring biasing means to vary the position of said cover plate and control the resonant frequency of said having a. ,generally doughnut-shaped recess `cut in zone' face. thereof ,and-a generally'concal reeA cess` .out :into the `other ,facef thereof andL-sym-Y metrcal with 'respect tof saidgrstw recess; said block lhaving a channel .along the. axis of saidrecessesand passing through-said block, afcathode and focusing cylinder insulatingly mountedjadjacent said' other block face for directingfaV .fo-v cused ibeam-fof electrons Ainto said conical' recess forpas'sage through saidV channel, Va Vnexiblercoyer 10 plaizezior4 said doughnut-shaped recess, saidcover plate vbeing rigidly .fastened .to sadblockaround .thefboundary of said :recess to form a cavity resonatorpsaidcover platehaving an Vaperture there-` through in line with sa'd channel andbeing flexible alongV the .axisof said channel, a backfocusnggplate dsposedadjacent said .coverplate and-having`I arr-.aperture aligned with said chan- Y ne1,: a reiecing plate ,disposedV beyond rsaid backfocusing plate, a vpush rod rgdlyfastened to Asaid coverA plate and-:passing Vthzr'ouglr'clearance L'apertures'in saidback-focusing and: reflecting plates, a bowed spring disposedbetween said push rod land said shell, said .spring being anchored on theL linside surfaces of -said shell, and means adapted to be controlled from the outside of said shell for controllingthe flexure of said spring to 'controli the resonant frequency ofV said cavity 

